Wet oxidation is a series of oxidative and hydrolysis reactions which occur at elevated temperatures and pressures, typically in an aqueous environment. Wet oxidation is a well-known process for use in purifying waste waters, such as sewage sludge and manufacturing waste process waters. Further, it is known that wet oxidation can be accomplished by use of a catalyst with an oxygen-containing gas at elevated temperatures and pressures. U.S. Pat. No. 4,141,828 to Okada et al., teaches a process of wet oxidation of ammonia-containing waste water by contacting the waste water with an oxygen-containing gas and a catalyst and subjecting the mixture to the elevated temperatures and pressures. U.S. Pat. No. 4,072,608 to Farha, Jr. et al., teaches a process for the purification of water polluted by organics and oxygen-containing compounds. This process comprises contacting the waste water and an oxygen-containing gas with an iron group metal promoted by a solid copper-magnesium-oxygen spinel structure catalyst at elevated temperatures and pressures. U.S. Pat. No. 4,062,772 to Box, Jr. et al. also relates to a process for the purification of organically polluted waters by contacting the waste waters with a solid copper-magnesium-oxygen catalyst promoted with bismuth and an oxygen-containing gas at elevated temperatures and pressures. U.S. Pat. No. 4,268,399 to Box, Jr. et al., relates to a process for oxidizing organically polluted waters by contacting the polluted waters with an oxygen-containing gas and a catalyst consisting of zinc, titanium, and oxygen.
None of these references teach a process of wet oxidation using copper (II) oxide (CuO) as the single oxygen source for the oxidizing reactions.
Accordingly, it is an object of this invention to provide a wet oxidation process, particularly for the detoxification of waste streams, utilizing copper (II) oxide as the single oxygen source for the reactions.
As a result of major environmental problems occurring today, inorganic and organic waste material that are generally carried in aqueous streams must be detoxified before disposal. Waste compounds that pose environmental disposal problems include cyanide-bearing solutions; halogenated hydrocarbons, such as pentachlorophenols prevalent in wood processing waste; hydrocarbon wastes from petrochemical plants and refineries, such as phenolic compounds; and dioxins. However, effective detoxification and destruction of the toxic waste materials require costly chemicals and/or elevated pressures which make such a system quite expensive.
The high pressures required for wet oxidation reactions have been previously achieved in autoclave-type reaction vessels which allow for agitation and mixing of the reaction components. However, such systems require large amounts of energy to achieve the required temperatures and pressures and to pump reaction components into the pressurized vessels. It was desirable to find a more economical way of achieving the required temperatures and pressures and moving reaction components. A vertical tube reactor configuration was considered as an economic means for achieving desired reaction conditions. U.S. Pat. No. 4,272,383 to McGrew, along with the various references cited therein, disclose such reactor configurations, along with particular processing conditions for treatment of particular wastes. Deep well reactors have been used to accomplish wet oxidation, and a vertical tube subsurface reactor environment useful for controlled chemical oxidation reactions was disclosed in U.S. Pat. No. 3,606,999 to Lawless, but this patent does not teach detoxification of hazardous waste. Use of a vertical tube reactor system could provide the necessary pressure by hydrostatic head pressure inherent in the system, but such reactors do not allow for agitation or mixing of the reaction components as they provide only "plug" or laminar flow. Since detoxification of many of the waste materials involves decomposition of molecules or complexes which are difficult to break, and thought to require agitation of the reaction mixture in order to achieve reasonably complete oxidation, the usefulness of a vertical tube reactor for this purpose was by no means certain. Surprisingly, however, the vertical tube reactor was found to be effective in achieving substantially complete detoxifying even on such stubborn materials as copper and silver complexes with cyanide. However, one disadvantage of the subsurface vertical tube reactor system is the introduction of an oxygen-containing gas at these depths. It would be advantageous to have a system where the oxygen source is contacted with the waste feed stream prior to downflowing the waste stream into the vertical tube reactor system.
Thus, an object of one embodiment of this invention is to provide an oxidation process for the detoxification of hazardous organic and inorganic waste contained in feed streams by using a vertical tube reactor system in which the only external oxygen source is non-gaseous copper (II) oxide.